Head-end device of distributed antenna system and method of operation thereof

ABSTRACT

A head-end device according to an embodiment includes: a plurality of base station interfacing units configured to interface each of transmission/reception signals that are exchanged between the head-end device and a plurality of base stations; and a head-end control unit configured to receive an upper interfacing unit signal transmitted from an upper base station interfacing unit from among the plurality of base station interfacing units, and sequentially transmit the received upper interfacing unit signal to a lower base station interfacing unit.

BACKGROUND 1. Field

One or more embodiments relate to a head-end device of a distributedantenna system and a method of operation thereof, and more particularly,to a head-end device of a distributed antenna system that can beimplemented with a more efficient structure by using a serialtransmission system in a head end, and a method of operating thehead-end device.

2. Description of the Related Art

Due to the development of mobile communication, the usage of mobilecommunication by users is rapidly increasing, and the users want to beprovided with a stable communication service without restriction of timeand space. However, it is difficult for a service provider to provide asmooth communication service to users because a shadow area exists dueto the limited output of the base station, the limitation of a locationof a base station, and the surrounding terrain. To solve the problem, adistributed antenna system (DAS) is being used.

The DAS is installed in an area where radio waves are not received orwhere radio waves are weak, such as inside buildings, undergroundbuildings, subways, tunnels, and apartment complexes in a residentialarea to extend a coverage of a base station by providing communicationservices to even a shadow area where signals of the base station aredifficult to reach. The DAS includes a head-end device communicativelyconnected to the base station and at least one remote device connectedto the head-end device through an optical transmission medium andcommunicatively connected to a user terminal.

SUMMARY

One or more embodiments include a head-end device of a distributedantenna system that can be implemented with a more efficient structureby using a serial transmission system in a head end, and a method ofoperating the head-end device.

According to one or more embodiments, a head-end device includes aplurality of base station interfacing units configured to interface eachof transmission/reception signals that are exchanged between thehead-end device and a plurality of base stations and a head-end controlunit configured to receive an upper interfacing unit signal transmittedfrom an upper base station interfacing unit from among the plurality ofbase station interfacing units, and sequentially transmit the receivedupper interfacing unit signal to a lower base station interfacing unit.

According to an example embodiment, the plurality of base stationinterfacing units are connected to each other in a cascade structurethrough the head-end control unit.

According to an example embodiment, each of the plurality of basestation interfacing units comprises: a combiner configured to, indownlink communication, combine the upper interfacing unit signaltransmitted from the upper base station interfacing unit through thehead-end control unit with a downlink signal directly received by thelower base station interfacing unit.

According to an example embodiment, a lowermost base station interfacingunit from among the plurality of base station interfacing units isconfigured to transmit serial downlink signals, in which all of downlinksignals received by each of the plurality of base station interfacingunits are combined, to a head-end optical transceiving unit through thehead-end control unit.

According to an example embodiment, the head-end device is a mainhead-end device, and the combiner of an uppermost base stationinterfacing unit from among the plurality of base station interfacingunits is configured to combine a downlink signal transmitted from a subhead-end device with a downlink signal directly received by theuppermost base station interfacing unit and output the combined signal.

According to an example embodiment, each of the plurality of basestation interfacing units, in uplink communication, is configured toseparate and output an uplink signal with respect to a correspondingbase station interfacing unit from the received upper interfacing unitsignal, and transmit the remaining uplink signal to a lower base stationinterfacing unit.

According to an example embodiment, an uppermost base stationinterfacing unit from among the plurality of base station interfacingunits is configured to receive serial uplink signals transmitted from ahead-end optical transceiving unit.

According to an example embodiment, the head-end device is a mainhead-end device, and a lowermost base station interfacing unit fromamong the plurality of base station interfacing units is configured totransmit the remaining uplink signal to a sub head-end device.

According to one or more embodiments, a method of operating a head-enddevice comprising: receiving an upper base station interfacing unitsignal transmitted from an upper base station interfacing unit through ahead-end control unit, combining the upper base station interfacing unitsignal with a downlink signal directly received by a corresponding basestation interfacing unit, and transmitting the combined signal to alower base station interfacing unit through the head-end control unit.

According to one or more embodiments, a method of operating a head-enddevice comprising: receiving an upper base station interfacing unitsignal transmitted from an upper base station interfacing unit through ahead-end control unit, distributing the upper base station interfacingunit signal to an uplink signal with respect to a corresponding basestation interfacing unit and the remaining uplink signal, andtransmitting the distributed remaining uplink signal to a lower basestation interfacing unit.

According to one or more example embodiments, the head-end deviceincludes a head-end control unit that receives serial downlink signaltransmitted from any one of a plurality of base station interfacingunits, and a plurality of head-end optical transceiving units thatreceive the serial downlink signal output from the head-end controlunit, distribute the received serial downlink signal, and transmit theserial downlink signal in parallel to a remote device or an extensiondevice, wherein one of the plurality of head-end optical transceivingunits receives the serial downlink signal and sequentially distributesthe serial downlink signal to the remaining head-end opticaltransceiving units.

According to an example embodiment, the one of the plurality of head-endoptical transceiving units may be an uppermost head-end opticaltransceiving unit from among the plurality of head-end opticaltransceiving units.

According to an example embodiment, each of the plurality of head-endoptical transceiving units may include a distributor that distributes anupper head-end optical transceiving unit signal transmitted from anupper head-end optical transceiving unit from among the plurality ofhead-end optical transceiving units to a signal to be transmitted to theremote device or the extension device and a signal to be transmitted toa lower head-end optical transceiving unit.

According to an example embodiment, each of the plurality of head-endoptical transceiving units may include a plurality of sub head-endoptical transceiving units, and one of the plurality of sub head-endoptical transceiving units may receive the serial downlink signal anddistribute the same to the remaining sub head-end optical transceivingunit.

According to one or more example embodiments, the head-end deviceincludes a plurality of head-end optical transceiving units thatsequentially combine uplink signals received in parallel from each ofremote devices or extension devices and output combined serial uplinksignal, and a head-end control unit that receives the serial uplinksignal transmitted from one of the plurality of head-end opticaltransceiving units and transmits the received serial uplink signal toone of a plurality of base station interfacing units.

According to an example embodiment, the one of the plurality of head-endoptical transceiving units may be a lowermost head-end opticaltransceiving unit from among the plurality of head-end opticaltransceiving units.

According to an example embodiment, each of the plurality of head-endoptical transceiving units may include a combiner that combines an upperhead-end optical transceiving unit signal transmitted from an upperhead-end optical transceiving unit from among the plurality of head-endoptical transceiving units and an uplink signal directly received by acorresponding head-end optical transceiving unit.

According to an example embodiment, each of the plurality of head-endoptical transceiving units may include a plurality of sub head-endoptical transceiving units, and a lower sub head-end opticaltransceiving unit from among the plurality of sub head-end opticaltransceiving units may combine a signal transmitted from an upper subhead-end optical transceiving unit and an uplink signal directlyreceived by the lower sub head-end optical transceiving unit and outputthe same.

According to one or more example embodiments, a method of operating ahead-end device includes transmitting serial downlink signal, in whichall of downlink signals received by each of a plurality of base stationinterfacing units are combined, to any one of a plurality of head-endoptical transceiving units through a head-end control unit, receivingthe serial downlink signal through the any one of the plurality ofhead-end optical transceiving units, and sequentially distributing thereceived serial downlink signal and transmitting the distributed serialdownlink signals in parallel to a remote device or an extension device.

According to one or more example embodiments, a method of operating ahead-end device includes receiving uplink signals transmitted inparallel from each of remote devices or extension devices, sequentiallycombining the received uplink signals, and transmitting the combinedserial uplink signal to any one of a plurality of base stationinterfacing units through a head-end control unit.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of a distributed antenna system according toan embodiment;

FIG. 2 is a view of a signal processing path of a main head-end devicein downlink communication in FIG. 1;

FIG. 3 is a view of a detailed signal processing path between aplurality of base station interfacing units and a head-end control unitin FIG. 2;

FIG. 4 is a view of a detailed signal processing path between a head-endcontrol unit and a plurality of head-end optical transceiving units inFIG. 2;

FIG. 5 is a view of a signal processing path of a main head-end devicein uplink communication in FIG. 1;

FIG. 6 is a view of a detailed signal processing path between aplurality of base station interfacing units and a head-end control unitin FIG. 5;

FIG. 7 is a view of a detailed signal processing path between a head-endcontrol unit and a plurality of head-end optical transceiving units inFIG. 5;

FIG. 8 is a flowchart of a method of operating the distributed antennasystem in downlink communication in FIG. 1;

FIG. 9 is a flowchart of a method of operating the distributed antennasystem in uplink communication in FIG. 1;

FIG. 10 is a flowchart of a method of operating the distributed antennasystem in downlink communication in FIG. 1; and

FIG. 11 is a flowchart of a method of operating the distributed antennasystem in uplink communication in FIG. 1.

DETAILED DESCRIPTION

The inventive concept may be variously modified and have various exampleembodiments, so that specific example embodiments will be illustrated inthe drawings and described in the detailed description. However, thisdoes not limit the inventive concept to specific example embodiments,and it should be understood that the inventive concept covers all themodifications, equivalents and replacements included within the idea andtechnical scope of the inventive concept.

In describing the inventive concept, in the following description, adetailed explanation of known related technologies may be omitted toavoid unnecessarily obscuring the subject matter of the inventiveconcept. In addition, numeral figures (for example, 1, 2, and the like)used during describing the specification are just identification symbolsfor distinguishing one element from another element.

Further, in the specification, if it is described that one component is“connected” or “accesses” the other component, it is understood that theone component may be directly connected to or may directly access theother component but unless explicitly described to the contrary, anothercomponent may be “connected” or “access” between the components.

In addition, terms including “unit”, “er”, “or”, “module”, and the likedisclosed in the specification mean a unit that processes at least onefunction or operation and this may be implemented by hardware orsoftware such as a processor, a micro processor, a micro controller, acentral processing unit (CPU), a graphics processing unit (GPU), anaccelerated Processing unit (APU), a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), and a field programmablegate array (FPGA) or a combination of hardware and software.Furthermore, the terms may be implemented in a form coupled to a memorythat stores data necessary for processing at least one function oroperation.

Moreover, it is intended to clarify that components in the specificationare distinguished in terms of primary functions of the components. Thatis, two or more components to be described below may be provided to becombined to one component or one component may be provided to be dividedinto two or more components for each more subdivided function. Inaddition, each of the respective components to be described below mayadditionally perform some or all functions among functions which othercomponents take charge of in addition to a primary function which eachcomponent takes charge of and some functions among the primary functionswhich the respective components take charge of are exclusively chargedby other components to be performed, of course.

The distributed antenna system according to an embodiment of theinventive concept improves a poor propagation environment in a building,improves a poor received signal strength indication (RSSI) and theoverall reception sensitivity of a mobile terminal, chip energy/otherinterferences (Ec/Io), and provides a mobile communication service toevery corner of the building so that a user of the mobile communicationservice can freely talk anywhere in the building.

The distributed antenna system according to an embodiment of theinventive concept may support the mobile communication standard usedworldwide. For example, the distributed antenna system may support atime division duplex (TDD) service as well as a frequency divisionduplex (FDD) service, a very-high frequency (VHF), an ultra-highfrequency (UHF), and frequencies of 700 MHz, 800 MHz, 850 MHz, 900 MHz,1900 MHz, 2100 MHz, and 2600 MHz bands. Furthermore, the distributedantenna system may support a number of mobile communication standardssuch as a typical analog mobile communication service, that is, anadvanced mobile phone service (AMPS), digital time-division multipleaccess (TDMA), code-division multiple access (CDMA), widebandcode-division multiple access (WCDMA), high-speed downlink packet access(HSDPA), long-term evolution (LTE), LTE-advanced (LTE-A), and so on.

Hereinafter, embodiments of the inventive concept will be described indetail in turn.

FIG. 1 is a block diagram of a distributed antenna system (DAS) 200according to an embodiment.

Referring to FIG. 1, the DAS 200 may include head-end devices 210-1 and210-2 that constitute a head-end node and are communicatively connectedto a plurality of base transceiver stations BTS 100-1 to 100-n, aplurality of remote devices 220 that constitute a remote node and arecommunicatively connected to a user terminal by being arranged at eachremote service location, and extension devices 230 that constitute anextension node, and a plurality of remote devices 240 connected to eachof the extension devices 230. The DAS 200 may be implemented as ananalog DAS. However, the inventive concept is not limited thereto.According to an embodiment, the DAS 200 may be implemented as a digitalDAS, and in some cases may be implemented as a mixed form thereof (e.g.,some nodes perform analog processing and the other nodes perform digitalprocessing). Hereinafter, a case where the DAS 200 is implemented as ananalog DAS will be described as an example.

Meanwhile, FIG. 1 shows an example of a topology of the DAS 200 andvarious variations are possible in the DAS 200 considering specificityof installation areas and application fields (e.g., in-building, asubway, a hospital, a stadium, etc.). That is, the number of thehead-end devices 210-1 and 210-2, the extension devices 230, and theremote devices 220 and 240, and a connection relationship between upperand lower ends thereof may be different from those of FIG. 1. Forexample, at least one extension device or remote device may be connectedto a lower end of any one of the remote devices 220 directly connectedto the head-end devices 210-1 and 210-2 or any one of the remote devices240 directly connected to the extension devices 230.

Also, the extension device 230 in the DAS 200 may be utilized when thenumber of branches of the head-end devices 210-1 and 210-2 is limitedcompared to the number of remote devices to be installed.

Each node in the DAS 200 and its function will be described in moredetail. First, the head-end devices 210-1 and 210-2 may serve as aninterface with a base station. FIG. 1 shows that each of the head-enddevices 210-1 and 210-2 is connected to first BTS BTS#1 to n^(th) BTSBTS#n (where n is a natural number of 2 or more). According to anembodiment, each of the head-end devices 210-1 and 210-2 may beconnected to a base station for each service frequency band of aspecific service provider or a base station for each sector. Accordingto another embodiment, the main head-end device 210-1 may compensate forcoverage by the sub head-end device 210-2.

In general, since a radio frequency (RF) signal transmitted from a basestation is a high-power signal, the head-end devices 210-1 and 210-2 mayattenuate such a high-power RF signal into a signal of power suitablefor processing at each node. The head-end devices 210-1 and 210-2 maylower a high-power RF signal for each frequency band or for each sectorto a low-power RF signal. The head-end devices 210-1 and 210-2 maycombine the low-power RF signals and may distribute the combined signalto the extension device 230 a or the remote device 220 a.

The extension device 230 may transmit the distributed combined signal tothe remote device 240 connected to the extension device 230.

Each of the remote devices 220 and 240 may separate the receivedcombined signal for each frequency band and perform signal processingsuch as amplification. Accordingly, each of the remote devices 220 and240 may transmit a base station signal to a user terminal in its servicecoverage through a service antenna (not shown).

Although FIG. 1 shows that the plurality of BTS 100-1 to 100-n and thehead-end devices 210-1 and 210-2 are connected to each other through anRF cable, and the head-end devices 210-1 and 210-2 and a lower end ofthe head-end devices 210-1 and 210-2 are connected to each other throughan optical cable, a signal transport medium between nodes may vary.

For example, at least one of between the head-end devices 210-1 and210-2 and the extension device 230, between the head-end devices 210-1and 210-2 and the remote device 220, between the extension device 230and the remote device 240 may be connected through an RF cable, atwisted cable, a UTP cable or the like in addition to the optical cable.

However, the following description will be made with reference toFIG. 1. Therefore, in the DAS 200, the head-end devices 210-1 and 210-2,the extension device 230, and the remote devices 220 and 240 may includean optical transceiver module for transmitting and receiving opticalsignals through electro-optical conversion/photoelectric conversion, andmay further include a wavelength division multiplexing (WDM) device whennodes are connected to each other by a single optical cable.

The DAS 200 may be connected to an external management device (notshown) such as a network management server or a network managementsystem (NMS) 300 or a network operation center (NOC) (not shown) via anetwork. Accordingly, an administrator may remotely monitor the statusand problem of each node of the DAS 200, and may remotely control theoperation of each node.

FIG. 2 is a view of a signal processing path of the main head-end device210-1 in downlink communication in FIG. 1. FIG. 3 is a view of adetailed signal processing path between a plurality of base stationinterfacing units 212-1 to 212-4 and a head-end control unit 214 in FIG.2. FIG. 4 is a view of a detailed signal processing path between thehead-end control unit 214 and a plurality of head-end opticaltransceiving units 216-1 to 216-4 in FIG. 2.

Referring to FIGS. 1 and 2, the main head-end device 210-1 may includethe plurality of base station interfacing units 212-1 to 212-4, thehead-end control unit 214, and the plurality of head-end opticaltransceiving units 216-1 to 216-4.

Although FIGS. 2 to 4 show a case where the main head-end device 210-1includes four interfacing units and four head-end optical transceivingunits for convenience of description, but the inventive concept is notlimited thereto. The number of interfacing units and head-end opticaltransceiving units may vary.

Furthermore, FIGS. 2 to 4 mainly describe a configuration used for adownlink communication process for convenience of description, and aconfiguration used for an uplink communication process is omitted.

Each of the plurality of base station interfacing units 212-1 to 212-4receives base station signals transmitted in parallel from each of theplurality of BTS 100-1 to 100-n in downlink communication. Each of theplurality of base station interfacing units 212-1 to 212-4 may interfacethe received base station signals with a signal suitable for processingat each node at a rear end of the plurality of base station interfacingunits 212-1 to 212-4. For example, each of the plurality of base stationinterfacing units 212-1 to 212-4 may attenuate and output the receivedbase station signals.

According to an embodiment, each of the plurality of base stationinterfacing units 212-1 to 212-4 may interface signals of differentfrequency bands.

The head-end control unit 214 may monitor a operation status of each ofthe components 212-1 to 212-4 and 216-1 to 216-4 in the main head-enddevice 210-1, or may control general operations of each of thecomponents 212-1 to 212-4 and 216-1 to 216-4 in the main head-end device210-1.

The head-end control unit 214 may receive an upper interfacing unitsignal transmitted from an upper base station interfacing unit (e.g.,the fourth base station interfacing unit 212-4) from among the pluralityof base station interfacing units 212-1 to 212-4, and may sequentiallytransmit the received upper interfacing unit signal to a lower basestation interfacing unit (e.g., the third base station interfacing unit212-3).

Herein, the term “upper base station interfacing unit” refers to a basestation interfacing unit located relatively ahead on a signal path ofdownlink communication or uplink communication, and the term “lower basestation interfacing unit” may refer to a base station interfacing unitlocated relatively behind on a signal path of downlink communication oruplink communication.

That is, since a signal path of the downlink communication is differentfrom that of the uplink communication, the “upper base stationinterfacing unit” in the downlink communication and “upper base stationinterfacing unit” in the uplink communication may different. Likewise,the “lower base station interfacing unit” in the downlink communicationand the “lower base station interfacing unit” in the uplinkcommunication may different.

Referring to FIGS. 2 and 3, each of the plurality of base stationinterfacing units 212-1 to 212-4 may include combiners 212-1A to 212-4Afor combining signals.

The fourth base station interfacing unit 212-4 is a frontmost basestation interfacing unit, that is, an uppermost base station interfacingunit, in which a downlink signal is input to the main head-end device210-1 in downlink communication.

A fifth downlink signal DL5 input from the sub head-end device 210-2 maybe input to the fourth base station interfacing unit 212-4 through thehead-end control unit 214.

The combiner 212-4A of the fourth base station interfacing unit 212-4may combine a fifth downlink signal DL5 transmitted from the subhead-end device 210-2 through the head-end control unit 214 and a basestation signal DL4 directly received by the fourth base stationinterfacing unit 212-4, and may output the combined signal DL4 and DL5.The downlink signals output from the fourth base station interfacingunit 212-4, that is, the upper interfacing unit signal DL4 and DL5 maybe transmitted to the third base station interfacing unit 212-3 throughthe head-end control unit 214.

The term “upper interfacing unit signal” herein may broadly refer to asignal transmitted from a relatively higher interfacing unit than thecorresponding interfacing unit. And the upper interfacing unit signalDL4 and DL5 may refer a combined signal which is combination of a fourthdownlink signal DL4 and a fifth downlink signal DL5.

The third base station interfacing unit 212-3 may receive the upperinterfacing unit signal DL4 and DL5 transmitted from an upper head-endcontrol unit, for example, the fourth base station interfacing unit212-4 through the head-end control unit 214. The combiner 212-3A of thethird base station interfacing unit 212-3 may combine the received upperinterfacing unit signal DL4 and DL5 and a base station signal DL3directly received by the third base station interfacing unit 212-3, andmay output the combined signal DL3, DL4, and DL5.

In the same manner, the second base station interfacing unit 212-2 maycombine a downlink signal DL2 directly received by the second basestation interfacing unit 212-2 to the upper interfacing unit signal DL3,DL4, and DL5, and may transmit the combined signal DL2, DL3, DL4, andDL5 to the first base station interfacing unit 212-1, which is alowermost base station interfacing unit, through the head-end controlunit 214.

In downlink communication, the first base station interfacing unit212-1, which is a lowermost base station interfacing unit, may transmitserial downlink signal, in which all of the downlink signals DL1, DL2,DL3, and DL4 received by each of the plurality of base stationinterfacing units 212-1 to 212-4 are combined, to the first head-endoptical transceiving unit 216-1 through the head-end control unit 214.

According to the embodiment, when there is the downlink signal DL5 inputfrom the sub head-end device 210-2, the first base station interfacingunit 212-1 may transmit serial downlink signal DL1, DL2, DL3, DL4, andDL5, in which the downlink signals DL1, DL2, DL3, and DL4 received byeach of the plurality of base station interfacing units 212-1 to 212-4and the downlink signal DL5 input from the sub head-end device 210-2 arecombined, to the first head-end optical transceiving unit 216-1 throughthe head-end control unit 214.

Referring again to FIG. 2, any one of the head-end optical transceivingunits 216-2 to 216-4, for example, the first head-end opticaltransceiving unit 216-1, may receive serial downlink signal transmittedfrom the first base station interfacing unit 212-1 and sequentiallydistribute the serial downlink signal to the remaining head-end opticaltransceiving units, for example, the second to fourth head-end opticaltransceiving units 216-2 to 216-4. Each of the plurality of head-endoptical transceiving units 216-1 to 216-4 may transmit in parallel thedistributed serial downlink signals to the remote device 220 or theextension device 230.

According to an embodiment, a head-end optical transceiving unitreceiving serial downlink signals in downlink communication may be anuppermost head-end optical transceiving unit from among a plurality ofhead-end optical transceiving units, for example, the first head-endoptical transceiving unit 216-1.

Referring to FIGS. 2 and 4, each of the plurality of head-end opticaltransceiving units 216-1 to 216-4 may include a plurality of subhead-end optical transceiving units 218-1 to 218-4 and 220-1 to 220-4.

Furthermore, each of the plurality of sub head-end optical transceivingunits 218-1 to 218-4 and 220-1 to 220-4 may include distributors 218-1Ato 218-4A and 220-1A to 220-4A.

The first sub head-end optical transceiving unit 218-1 of the firsthead-end optical transceiving unit 216-1 receiving serial downlinksignal may distribute the serial downlink signals in two, and maytransmit one signal to the remote device 220 or extension device 230,and the other signal to the second sub head-end optical transceivingunit 220-1.

The second sub head-end optical transceiving unit 220-1 of the firsthead-end optical transceiving unit 216-1 may distribute the signalsreceived from the first sub head-end optical transceiving unit 218-1again in two, and may transmit one signal to the remote device 220 orextension device 230, and the other signal to the second head-endoptical transceiving unit 216-2.

In the same manner, each of the plurality of head-end opticaltransceiving units 216-1 to 216-4 may sequentially distribute an upperhead end optical transceiving unit signal transmitted from an upperhead-end optical transceiving unit from among the plurality of head-endoptical transceiving units 216-1 to 216-4 to a signal to be transmittedto the remote device 220 or the extension device 230 and a signal to betransmitted to a lower head-end optical transceiving unit from among theplurality of head-end optical transceiving units 216-1 to 216-4.

According to an embodiment, a relationship between an upper head-endoptical transceiving unit and a lower head-end optical transceiving unitmay be directly applied to a relationship between an upper sub head-endoptical transceiving unit and a lower sub head-end optical transceivingunit. For example, any one of the plurality of sub head-end opticaltransceiving units (e.g., 218-1 and 220-1), for example, the first subhead-end optical transceiving unit 218-1, may receive serial downlinksignal and sequentially distribute the serial downlink signals to theremaining sub head-end optical transceiving unit, for example, thesecond sub head-end optical transceiving unit 220-1.

FIG. 5 is a view of a signal processing path of the main head-end device210-1 in uplink communication in FIG. 1. FIG. 6 is a view of a detailedsignal processing path between a plurality of base station interfacingunits and a head-end control unit in FIG. 5. FIG. 7 is a view of adetailed signal processing path between a head-end control unit and aplurality of head-end optical transceiving units in FIG. 5.

Although FIGS. 5 to 7 show a case where the main head-end device 210-1includes four interfacing units and four head-end optical transceivingunits for convenience of description, but the inventive concept is notlimited thereto. The number of interfacing units and head-end opticaltransceiving units may vary.

Furthermore, FIGS. 5 to 7 mainly describe a configuration used for anuplink communication process for convenience of description, and aconfiguration used for a downlink communication process is omitted.

In uplink communication, an uppermost base station interfacing unit, forexample, the first base station interfacing unit 212-1, from among theplurality of base station interfacing units 212-1 to 212-4 may receiveserial uplink signal transmitted from the first head-end opticaltransceiving unit 216-1 through the head-end control unit 214.

Each of the plurality of base station interfacing units 212-1 to 212-4may distribute an upper interfacing unit signal to an uplink signal withrespect to a corresponding base station interfacing unit and theremaining uplink signals.

Referring to FIGS. 5 and 6, each of the plurality of base stationinterfacing units 212-1 to 212-4 may include band-pass filters 212-1B to212-4B and distributors 212-1C to 212-4C for distributing signals.

The first base station interfacing unit 212-1 is a frontmost basestation interfacing unit, that is, an uppermost base station interfacingunit, to which serial uplink signal is input in uplink communication.

Serial uplink signal UL1, UL2, UL3, UL4, and UL5 transmitted from thefirst head-end optical transceiving unit 216-1 may be input to the firstbase station interfacing unit 212-1.

The distributor 212-1C of the first base station interfacing unit 212-1may distribute the received serial uplink signal UL1, UL2, UL3, UL4, andUL5 to the uplink signal UL1 corresponding to the first base stationinterfacing unit 212-1 and the remaining uplink signal UL2, UL3, UL4,and UL5. According to an embodiment, the remaining uplink signal UL2,UL3, UL4, and UL5 may be a serial signal. The first uplink signal UL1distributed by the distributor 212-1C may be transmitted to at least oneof the plurality of BTS 100-1 to 100-n through the band-pass filter212-1B. The remaining uplink signal UL2, UL3, UL4, and UL5 distributedby the distributor 212-1C may be transmitted to the second base stationinterfacing unit 212-2, which is a lower base station interfacing unitof the first base station interfacing unit 212-1, through the head endcontrol unit 214.

The second base station interfacing unit 212-2 may receive upperinterfacing unit signal (that is, the remaining uplink signal UL2, UL3,UL4, and UL5) from the first base station interfacing unit 212-1, whichis an upper base station interfacing unit, through the head end controlunit 214.

The distributor 212-2C of the second base station interfacing unit 212-2may distribute the received upper interfacing unit signal UL2, UL3, UL4,and UL5 to the uplink signal UL2 corresponding to the second basestation interfacing unit 212-2 and the remaining uplink signal UL3, UL4,and UL5. According to an embodiment, the remaining uplink signal UL3,UL4, and UL5 may be a serial signal. The second uplink signal UL2distributed by the distributor 212-2C may be transmitted to at least oneof the plurality of BTS 100-1 to 100-n through the band-pass filter212-2B.

In the same manner, the third base station interfacing unit 212-3 andthe fourth base station interfacing unit 212-4 also distribute an upperbase station interfacing unit signal to an uplink signal with respect toa corresponding base station interfacing unit and the remaining uplinksignal, and may transmit the remaining uplink signal to a lower basestation interfacing unit through the head-end control unit 214.

According to an embodiment, the distributor 212-4C of the fourth basestation interfacing unit 212-4 may transmit the remaining uplink signalUL5 to the sub-head end device 210-2 through the head-end control unit214.

Referring again to 5, each of the plurality of head-end opticaltransceiving units 216-1 to 216-4 may sequentially combine uplinksignals received in parallel from the remote device 220 or the extensiondevice 230. The combined serial uplink signal may be output from thefirst head-end optical transceiving unit 216-1 which is a lowermosthead-end optical transceiving unit of the plurality of head-end opticaltransceiving units 216-1 to 216-4.

Referring to FIGS. 5 and 7, each of the plurality of head-end opticaltransceiving units 216-1 to 216-4 may include the plurality of subhead-end optical transceiving units 218-1 to 218-4 and 220-1 to 220-4.

Furthermore, each of the plurality of sub head-end optical transceivingunits 218-1 to 218-4 and 220-1 to 220-4 may include combiners 218-1B to218-4B and 220-1B to 220-4B.

Each of the plurality of sub head-end optical transceiving units 218-1to 218-4 and 220-1 to 220-4 may receive uplink signals transmitted inparallel from the remote devices 220 or the extension devices 230.

Each of the plurality of sub head-end optical transceiving units 218-1to 218-4 and 220-1 to 220-4 may sequentially combine the uplink signalsreceived in parallel with from the second sub head-end opticaltransceiving unit 220-4 of the fourth head-end optical transceiving unit216-4 which is an uppermost head-end optical transceiving unit to thefirst sub head-end optical transceiving unit 218-1 of the first head-endoptical transceiving unit 216-1 which is a lowermost head-end opticaltransceiving unit.

The combined serial uplink signal may be transmitted to the head-endcontrol unit 214 by the first head-end optical transceiving unit 216-1which is a lowermost head-end optical transceiving unit. In particular,the combined serial uplink signal may be transmitted to the head-endcontrol unit 214 by the first sub head-end optical transceiving unit218-1 of the first head-end optical transceiving unit 216-1 which is alowermost head-end optical transceiving unit.

FIG. 8 is a flowchart of a method of operating the DAS 200 in downlinkcommunication in FIG. 1.

Referring to FIGS. 1 to 4 and 8, in operation S10, each of the pluralityof base station interfacing units 212-1 to 212-4 may receive an upperbase station interfacing unit signal transmitted from an upper basestation interfacing unit.

For example, the third base station interfacing unit 212-3 may receiveupper base station interfacing unit signal DL4 and DL5 from the fourthbase station interfacing unit 212-4 which is an upper base stationinterfacing unit.

In operation S12, each of the plurality of base station interfacingunits 212-1 to 212-4 may combine an upper base station interfacing unitsignal with a downlink signal directly received by a corresponding basestation interfacing unit.

For example, the third base station interfacing unit 212-3 may combinethe upper base station interfacing unit signal DL4 and DL5 with thedownlink signal DL3 directly received by a corresponding base stationinterfacing unit, that is, the third base station interfacing unit212-3.

In operation S14, each of the plurality of base station interfacingunits 212-1 to 212-4 may transmit the combined signal to a lower basestation interfacing unit through the head-end control unit 214.

For example, the third base station interfacing unit 212-3 may transmitthe combined signal DL3, DL4, and DL5 to a lower base stationinterfacing unit, that is, the second base station interfacing unit212-2, through the head-end control unit 214.

FIG. 9 is a flowchart of a method of operating the DAS 200 in uplinkcommunication in FIG. 1.

Referring to FIGS. 1, 5 to 7 and 8, in operation S20, each of theplurality of base station interfacing units 212-1 to 212-4 may receivean upper base station interfacing unit signal.

For example, the third base station interfacing unit 212-3 may receiveupper base station interfacing unit signal UL3, UL4, and UL5 ? from thesecond base station interfacing unit 212-2 which is an upper basestation interfacing unit.

In operation S22, each of the plurality of base station interfacingunits 212-1 to 212-4 may distribute an upper base station interfacingunit signal to an uplink signal with respect to a corresponding basestation interfacing unit and the remaining uplink signal.

For example, the third base station interfacing unit 212-3 maydistribute the upper base station interfacing unit signal UL3, UL4, andUL5 to the uplink signal UL3 with respect to a corresponding basestation interfacing unit, that is, the third base station interfacingunit 212-3, and the remaining uplink signal UL4 and UL5.

In operation S24, each of the plurality of base station interfacingunits 212-1 to 212-4 may transmit the distributed remaining signal to alower base station interfacing unit through the head-end control unit214.

For example, the third base station interfacing unit 212-3 may transmitthe distributed remaining uplink signal UL4 and UL5 to a lower basestation interfacing unit, that is, the fourth base station interfacingunit 212-4, through the head-end control unit 214.

FIG. 10 is a flowchart of a method of operating the DAS 200 in downlinkcommunication in FIG. 1.

Referring to FIGS. 1 to 4 and 10, in operation S30, one of the pluralityof base station interfacing units 212-1 to 212-4, for example, the firstbase station interfacing unit 212-1, may transmit serial downlink signalthrough the head-end control unit 214.

In operation S32, one of the plurality of head-end optical transceivingunits 216-1 to 216-4, for example, the first head-end opticaltransceiving unit 216-1, may receive serial downlink signal.

In operation S34, each of the plurality of head-end optical transceivingunits 216-1 to 216-4 may sequentially distribute the received serialdownlink signal and transmit the distributed signals in parallel to theremote device 220 or the extension device 230.

FIG. 11 is a flowchart of a method of operating the DAS 200 in uplinkcommunication in FIG. 1.

Referring to FIGS. 1, 5 to 7 and 11, in operation S40, each of theplurality of head-end optical transceiving units 216-1 to 216-4 mayreceive uplink signals transmitted in parallel from each of the remotedevices 220 or the extension devices 230.

In operation S42, the plurality of head-end optical transceiving units216-1 to 216-4 may sequentially combine the received uplink signals.

According to an embodiment, each of the plurality of head-end opticaltransceiving units 216-1 to 216-4 may sequentially combine the uplinksignals with from an upper head-end optical transceiving unit, forexample, the fourth head-end optical transceiving unit 216-4, to a lowerhead-end optical transceiving unit, for example, the first head-endoptical transceiving unit 216-1.

In operation S44, any one of the plurality of head-end opticaltransceiving units 216-1 to 216-4, for example, the first head-endoptical transceiving unit 216-1, may transmit combined serial uplinksignal to any one of the base station interfacing units 212-2 to 212-4,for example, the first base station interfacing unit 212-1.

The method and device according to embodiments of the inventive conceptmay simplify a circuit of a head end by using a serial transmissionmethod in a head end, thereby realizing a head end with a more efficientstructure.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the disclosure as defined by thefollowing claims.

What is claimed is:
 1. A head-end device comprising: a plurality of basestation interfaces configured to interface downlink signals receivedfrom a plurality of base stations; and a head-end control unitconfigured to receive an upper interface signal transmitted from anupper base station interface from among the plurality of base stationinterfaces, and transmit the received upper interface signal to a lowerbase station interface, wherein each of the plurality of base stationinterfaces includes a combiner configured to, in downlink communication,combine the upper interface signal transmitted from the upper basestation interface through the head-end control unit with a downlinksignal directly received by the lower base station interface.
 2. Thehead-end device of claim 1, wherein the plurality of base stationinterfaces are connected to each other in a cascade structure throughthe head-end control unit.
 3. The head-end device of claim 1, whereinthe head-end control unit sequentially transmits the received upperinterface signal to the lower base station interface.
 4. The head-enddevice of claim 1, wherein a lowermost base station interface from amongthe plurality of base station interfaces is configured to transmitserial downlink signals, in which all of the downlink signals receivedby each of the plurality of base station interfaces are combined, to ahead-end optical transceiving unit through the head-end control unit. 5.The head-end device of claim 1, wherein the head-end device is a mainhead-end device, and the combiner of an uppermost base station interfacefrom among the plurality of base station interfaces is configured tocombine a downlink signal transmitted from a sub head-end device with adownlink signal directly received by the uppermost base stationinterface and output the combined signal.
 6. A head-end devicecomprising: a plurality of base station interfaces configured tointerface uplink signals transmitted to a plurality of base stations;and a head-end control unit configured to receive an upper interfacesignal transmitted from an upper base station interface from among theplurality of base station interfaces, and transmit the received upperinterface signal to a lower base station interface, wherein each of theplurality of base station interfaces, in uplink communication, isconfigured to separate and output an uplink signal with respect to acorresponding base station interface from the received upper interfacesignal, and transmit a remaining uplink signal to a lower base stationinterface.
 7. The head-end device of claim 6, wherein an uppermost basestation interface from among the plurality of base station interfaces isconfigured to receive serial uplink signals transmitted from a head-endoptical transceiving unit.
 8. The head-end device of claim 7, whereinthe head-end device is a main head-end device, and a lowermost basestation interface from among the plurality of base station interfaces isconfigured to transmit the remaining uplink signal to a sub head-enddevice.
 9. A method of operating a head-end device, the methodcomprising: receiving an upper base station interface signal transmittedfrom an upper base station interface through a head-end control unit;combining the upper base station interface signal with a downlink signaldirectly received by a corresponding base station interface; andtransmitting the combined signal to a lower base station interfacethrough the head-end control unit.
 10. A method of operating a head-enddevice, the method comprising: receiving an upper base station interfacesignal transmitted from an upper base station interface through ahead-end control unit; distributing the upper base station interfacesignal to an uplink signal with respect to a corresponding base stationinterface and a remaining uplink signal; and transmitting thedistributed remaining uplink signal to a lower base station interface.